WO2022113277A1 - Gas-phase reduction apparatus for carbon dioxide, and method for producing porous reduction electrode-supported electrolyte membrane - Google Patents

Gas-phase reduction apparatus for carbon dioxide, and method for producing porous reduction electrode-supported electrolyte membrane Download PDF

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WO2022113277A1
WO2022113277A1 PCT/JP2020/044254 JP2020044254W WO2022113277A1 WO 2022113277 A1 WO2022113277 A1 WO 2022113277A1 JP 2020044254 W JP2020044254 W JP 2020044254W WO 2022113277 A1 WO2022113277 A1 WO 2022113277A1
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electrode
reduction
electrolyte membrane
porous
carbon dioxide
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French (fr)
Japanese (ja)
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紗弓 里
裕也 渦巻
晃洋 鴻野
武志 小松
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日本電信電話株式会社
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Priority to US18/254,087 priority patent/US20230416933A1/en
Priority to PCT/JP2020/044254 priority patent/WO2022113277A1/en
Publication of WO2022113277A1 publication Critical patent/WO2022113277A1/en

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    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/60—Constructional parts of cells
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/50—Processes
    • C25B1/55—Photoelectrolysis
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
    • C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
    • C25B11/031—Porous electrodes
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
    • C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
    • C25B11/031—Porous electrodes
    • C25B11/032—Gas diffusion electrodes
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B13/00—Diaphragms; Spacing elements
    • C25B13/02—Diaphragms; Spacing elements characterised by shape or form
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B15/00—Operating or servicing cells
    • C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B3/00—Electrolytic production of organic compounds
    • C25B3/20—Processes
    • C25B3/25—Reduction
    • C25B3/26—Reduction of carbon dioxide
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
    • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
    • C25B9/21—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms two or more diaphragms
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
    • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
    • C25B9/23—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms comprising ion-exchange membranes in or on which electrode material is embedded
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/50—Cells or assemblies of cells comprising photoelectrodes; Assemblies of constructional parts thereof

Definitions

  • the present invention relates to a carbon dioxide gas phase reducing device and a method for producing a porous reducing electrode-supported electrolyte membrane.
  • the carbon dioxide to be reduced dissolves in the aqueous solution in the reduction tank, reaches the reduction electrode, and is reduced on the surface of the reduction electrode.
  • an aqueous solution is used as a medium for carbon dioxide, there is a limit to the concentration of carbon dioxide that can be dissolved in the aqueous solution, and the diffusion resistance of carbon dioxide in the aqueous solution is large, so that it can be supplied to the reducing electrode.
  • the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique capable of improving the efficiency of a carbon dioxide reduction reaction in a carbon dioxide gas phase reduction device.
  • the carbon dioxide gas phase reduction device includes an oxide tank including an oxidation electrode, a reduction tank adjacent to the oxide tank and supplying carbon dioxide to the inside of the empty space, the oxide tank and the reduction.
  • the porous reduction electrode-supporting electrolyte membrane is provided with a porous reduction electrode-supporting electrolyte membrane arranged between the tank and the porous reduction electrode-supporting electrolyte membrane, and the porous reduction electrode-supporting electrolyte membrane is formed by dispersing the first electrolyte membrane inside the voids.
  • the porous reducing electrode support is arranged between an oxide tank including an oxide electrode and a reduction tank in which carbon dioxide is supplied to the inside of the empty space.
  • a step of impregnating a porous reducing electrode into an electrolyte dispersion in which a polymer material constituting the electrolyte membrane is dispersed, and the porous reducing electrode impregnated in the electrolyte dispersion is performed.
  • FIG. 1 is a diagram showing a configuration example of a carbon dioxide gas phase reducing device according to Example 1.
  • FIG. 2 is a diagram showing a method for producing a porous reducing electrode-supported electrolyte membrane.
  • FIG. 3 is a diagram showing a state in which an electrolyte membrane is dispersed and formed in the porous reducing electrode.
  • FIG. 4 is a diagram showing a configuration example of a carbon dioxide gas phase reducing device according to Example 9.
  • FIG. 5 is a diagram showing a configuration example of a carbon dioxide gas phase reducing device according to Comparative Example 1.
  • FIG. 6 is a diagram showing a configuration example of a carbon dioxide gas phase reducing device according to Comparative Example 2.
  • FIG. 7 is a diagram showing a state in which the electrolyte membrane is dispersed and formed in an island shape in the porous reducing electrode.
  • An object of the present invention is to provide a technique capable of improving the efficiency of a carbon dioxide reduction reaction in a carbon dioxide gas phase reduction device.
  • the present invention has the following features as compared with the conventional carbon dioxide gas phase reducing device.
  • the first feature is that the inside of the reduction tank is filled with carbon dioxide in the gas phase, and the carbon dioxide in the gas phase is directly supplied to the reduction electrode.
  • the concentration of carbon dioxide increases in the reduction tank, and the diffusion resistance of carbon dioxide decreases.
  • the amount of carbon dioxide supplied to the reducing electrode is increased, and the efficiency of the carbon dioxide reduction reaction on the reducing electrode can be improved.
  • the three-phase interface consisting of [electrolyte membrane-porous reducing electrode-gas phase carbon dioxide] is the bonding surface between the electrolyte membrane and the porous reducing electrode. It will be limited to the top only. Therefore, it is further provided with a third feature.
  • the third feature is that the electrolyte membrane is dispersed and formed inside the voids of the porous reducing electrode. As a result, the reaction field of the carbon dioxide gas phase reduction reaction is increased, so that the efficiency of the carbon dioxide reduction reaction on the porous reducing electrode can be improved.
  • the present invention directly supplies carbon dioxide in the gas phase to the porous reducing electrode-supported electrolyte membrane in which the electrolyte membrane is bonded to the porous reducing electrode formed by dispersing the electrolyte membrane inside the voids. It is characterized by. Due to this feature, it is possible to improve the efficiency of the reduction reaction of carbon dioxide on the reduction electrode.
  • FIG. 1 is a diagram showing a configuration example of the carbon dioxide gas phase reducing device 100 according to the first embodiment.
  • the gas phase reduction device 100 is a reduction device (artificial photosynthesis device) that causes a reduction reaction of carbon dioxide at the reduction electrode by irradiating the oxidation electrode with light.
  • a gas phase reducing device 100 it is simply referred to as a gas phase reducing device 100.
  • the gas phase reducing device 100 includes an oxidation tank 1 and a reduction tank 4 formed by dividing the internal space of one housing into two.
  • the oxide tank 1 is filled with the aqueous solution 3, and the oxide electrode 2 made of a semiconductor or a metal complex is inserted into the aqueous solution 3.
  • the reduction tank 4 adjacent to the oxidation tank 1 is filled with carbon dioxide gas or a gas containing carbon dioxide in the empty space.
  • the oxide electrode 2 is a compound that exhibits photoactivity and redox activity, such as a nitride semiconductor, titanium oxide, amorphous silicon, a ruthenium complex, and a rhenium complex.
  • the aqueous solution 3 is, for example, a potassium hydrogen carbonate aqueous solution, a sodium hydrogen carbonate aqueous solution, a potassium chloride aqueous solution, a sodium chloride aqueous solution, a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, a rubidium hydroxide aqueous solution, or a cesium hydroxide aqueous solution.
  • a porous reducing electrode 5 formed by dispersing an electrolyte membrane (first electrolyte membrane) in the voids and an electrolyte membrane (second electrolyte membrane) 6 are formed between the oxidation tank 1 and the reduction tank 4.
  • the porous reducing electrode support type electrolyte membrane 20 to which the above is bonded is arranged.
  • the electrolyte membrane 6 is arranged on the oxidation tank 1 side, and the porous reduction electrode 5 is arranged on the reduction tank 4 side.
  • the oxide electrode 2 and the porous reduction electrode 5 are connected by a conducting wire 7.
  • a tube 8 is inserted into the oxidation tank 1 in order to allow helium to flow into the aqueous solution 3 in the oxidation tank 1. Since carbon dioxide flows into the reduction tank 4, a gas input port 9 is formed at the bottom of the reduction tank 4. Further, in order to operate the gas phase reduction device 100, the light source 10 is arranged to face the oxide electrode 2.
  • the light source 10 is, for example, a xenon lamp, a pseudo-solar light source, a halogen lamp, a mercury lamp, sunlight, or a combination thereof.
  • porous reducing electrode support type electrolyte membrane 20 A method for producing the porous reducing electrode support type electrolyte membrane 20 will be described.
  • the porous reducing electrode support type electrolyte membrane 20 is formed by joining the porous reducing electrode 5 and the electrolyte membrane 6.
  • the porous reducing electrode 5 is, for example, copper, platinum, gold, silver, indium, palladium, gallium, nickel, tin, cadmium, a porous body of an alloy thereof, silver oxide, copper oxide, copper oxide (II), oxidation. It is a porous body such as nickel, indium oxide, tin oxide, tungsten oxide, tungsten oxide (VI), and copper oxide.
  • the porous reducing electrode 5 may be a porous metal complex having a metal ion and an anionic ligand.
  • the electrolyte membrane 6 is, for example, Nafion (trademark registration), Foreblue, and Aquivion, which are electrolyte membranes having a skeleton composed of carbon and fluorine.
  • the electrolyte membrane 6 may be Celemion or Neosepta, which is an electrolyte membrane having a hydrocarbon-based skeleton.
  • Example 1 a copper porous body having a thickness of 1 mm and a porosity of 98% was used as the porous reducing electrode 5.
  • the electrolyte membrane 6 Nafion, which is a cation exchange membrane, was used.
  • the Nafion dispersion prepared in% was used.
  • the solvent used for dilution is, for example, pure water, a lower alcohol, or a mixture thereof. In Example 1, pure water was used.
  • the electrolyte membrane 6 is previously immersed in boiling nitric acid and boiling pure water, respectively.
  • the porous reducing electrode 5 is impregnated with an electrolyte dispersion liquid (electrolyte content: 0.05 wt.%) In which a polymer material constituting an electrolyte membrane is dispersed.
  • the porous reducing electrode 5 impregnated with the electrolyte dispersion was placed on the electrolyte membrane 6 immersed in boiling nitric acid and boiling pure water, respectively, and the sample was placed on two copper plates as shown in FIG. It is arranged between 30a and 30b.
  • this sample is placed between the hot plates 40a and 40b of the thermocompression bonding device (hot press machine), and while heating under the condition of a heating temperature of 150 ° C., it is applied to the upper surface of the porous reducing electrode 5. Apply pressure vertically downward (against the electrode surface) and leave it for 3 minutes. The sample is then quickly cooled and removed. As a result, it is possible to obtain the porous reducing electrode support type electrolyte membrane 20 in which the porous reducing electrode 5 and the electrolyte membrane 6 are bonded.
  • the thickness of the porous reduction electrode 5 after thermocompression bonding was 0.2 mm, and the porosity was 90%.
  • the electrolyte membrane (first electrolyte membrane) 60 is dispersed and formed on the surface and the inside of the porous reducing electrode 5.
  • the electrolyte membrane 60 dispersedly formed at the interface between the porous reducing electrode 5 and the electrolyte membrane (second electrolyte membrane) 6 adheres to each other, and the electrolyte membrane 60 dispersedly formed inside the porous reducing electrode 5 Since a three-phase interface composed of the porous reduction electrode 5 and the carbon dioxide in the gas phase is formed, the reaction field of the gas phase reduction reaction of carbon dioxide is increased, and the reduction reaction of carbon dioxide is efficiently performed at the three-phase interface. proceed.
  • Electrochemical measurement and gas / liquid production amount measurement Electrochemical measurement and gas / liquid production amount measurement will be described.
  • a 300 W high-pressure xenon lamp (wavelength 450 nm or more cut, illuminance 6.6 mW / cm 2 ) is used as the light source 10, and the surface on which the oxidation assist catalyst of the semiconductor optical electrode of the oxide electrode 2 is formed (the surface on which NiO is formed). ) was fixed so as to be the irradiation surface.
  • the light irradiation area of the oxide electrode 2 was set to 2.5 cm 2 .
  • the oxide electrode 2 was uniformly irradiated with light using the light source 10. By irradiating the oxide electrode 2 with light, electrons flow between the oxide electrode 2 and the porous reduction electrode 5.
  • the current value between the oxide electrode 2 and the porous reduction electrode 5 at the time of light irradiation was measured with an electrochemical measuring device (1287 type potato galvanostat manufactured by Solartron).
  • the gas and liquid in the oxidation tank 1 and the reduction tank 4 were collected at an arbitrary time during light irradiation, and the reaction products were analyzed by a gas chromatograph, a liquid chromatograph, and a gas chromatograph mass spectrometer. As a result, it was confirmed that oxygen was generated in the oxidation tank 1 and hydrogen, carbon monoxide, formic acid, methane, methanol, ethanol and ethylene were produced in the reduction tank 4.
  • Example 2 In Example 2, in the production of the porous reducing electrode-supported electrolyte membrane 20, the electrolyte content of the electrolyte dispersion in step 1 was set to 0.1 wt. I made it to%. All other conditions are the same as in Example 1.
  • Example 4 In Example 4, in the production of the porous reducing electrode support type electrolyte membrane 20, the electrolyte content of the electrolyte dispersion liquid in step 1 was 1.0 wt. I made it to%. All other conditions are the same as in Example 1.
  • Example 5 In Example 5, in the production of the porous reducing electrode-supported electrolyte membrane 20, the electrolyte content of the electrolyte dispersion in step 1 was 5.0 wt. I made it to%. All other conditions are the same as in Example 1.
  • Example 6 In Example 6, a copper porous body having a thickness of 1 mm and a porosity of 90% was used in the production of the porous reducing electrode-supported electrolyte membrane 20. The thickness of the porous reducing electrode 5 after thermocompression bonding was 0.2 mm, and the porosity was 50%. All other conditions are the same as in Example 1.
  • Example 7 In Example 7, a copper porous body having a thickness of 1 mm and a porosity of 85% was used in the production of the porous reducing electrode-supported electrolyte membrane 20. The thickness of the porous reducing electrode 5 after thermocompression bonding was 0.2 mm, and the porosity was 25%. All other conditions are the same as in Example 1.
  • Example 8 In Example 8, a copper porous body having a thickness of 1 mm and a porosity of 81% was used in the production of the porous reducing electrode-supported electrolyte membrane 20. The thickness of the porous reducing electrode 5 after thermocompression bonding was 0.2 mm, and the porosity was 5%. All other conditions are the same as in Example 1.
  • FIG. 4 is a diagram showing the configuration of the carbon dioxide gas phase reducing device 100 according to the ninth embodiment.
  • the carbon dioxide gas phase reduction device 100 is an apparatus (electrolytic reduction reaction apparatus) for an electrolytic reduction reaction of carbon dioxide in the gas phase. Hereinafter, it is simply referred to as a gas phase reducing device 100.
  • a porous reducing electrode 5 formed by dispersing an electrolyte membrane (first electrolyte membrane) in the voids and an electrolyte membrane (second electrolyte membrane) 6 are formed between the oxidation tank 1 and the reduction tank 4.
  • the porous reducing electrode support type electrolyte membrane 20 to which the above is bonded is arranged.
  • the electrolyte membrane 6 is arranged on the oxidation tank 1 side, and the porous reduction electrode 5 is arranged on the reduction tank 4 side.
  • the oxide electrode 2 and the porous reduction electrode 5 are connected by a conducting wire 7.
  • Specific examples of the porous reducing electrode 5 and the electrolyte membrane 6 are the same as in Example 1.
  • a tube 8 is inserted into the oxidation tank 1 in order to allow helium to flow into the aqueous solution 3 in the oxidation tank 1. Since carbon dioxide flows into the reduction tank 4, a gas input port 9 is formed at the bottom of the reduction tank 4. Further, in order to operate the gas phase reduction device 100, the power supply 11 is connected to the lead wire 7.
  • porous reducing electrode support type electrolyte membrane 20 is produced by the same procedure as in Example 1.
  • Electrochemical measurement and gas / liquid production amount measurement Electrochemical measurement and gas / liquid production amount measurement will be described.
  • the oxidation tank 1 is filled with the aqueous solution 3.
  • Platinum manufactured by Niraco
  • Niraco was used for the oxide electrode 2.
  • About 0.55 cm 2 of the surface area of the oxidation electrode 2 was installed in the oxide tank 1 so as to be immersed in the aqueous solution 3.
  • the aqueous solution 3 was a 1.0 mol / L potassium hydroxide aqueous solution.
  • Helium was poured into the oxidation tank 1 from the tube 8 and carbon dioxide was poured into the reduction tank 4 from the gas input port 9 at a flow rate of 5 ml / min and a pressure of 0.18 MPa, respectively.
  • the carbon dioxide reduction reaction can proceed at the three-phase interface composed of [electrolyte membrane-copper (porous reduction electrode) -gas phase carbon dioxide] in the porous reduction electrode-supported electrolyte membrane 20. can.
  • the area of the porous reducing electrode 5 to which carbon dioxide is directly supplied is about 6.25 cm 2 .
  • the oxidation electrode 2 and the porous reduction electrode 5 are connected by a lead wire 7 via a power source 11, and a voltage of 2.5 V is applied. It was applied and electrons were flown.
  • the current value between the oxide electrode 2 and the porous reduction electrode 5 when a voltage of 2.5 V was applied was measured by an electrochemical measuring device.
  • the gas and liquid in the oxidation tank 1 and the reduction tank 4 were sampled at an arbitrary time while the voltage was applied, and the reaction products were analyzed by a gas chromatograph, a liquid chromatograph, and a gas chromatograph mass spectrometer. As a result, it was confirmed that oxygen was generated in the oxidation tank 1 and hydrogen, carbon monoxide, formic acid, methane, methanol, ethanol and ethylene were produced in the reduction tank 4.
  • Example 10 In Example 10, in the production of the porous reducing electrode support type electrolyte membrane 20, the electrolyte content of the electrolyte dispersion liquid in step 1 was set to 0.1 wt. I made it to%. All other conditions are the same as in Example 9.
  • Example 11 In Example 11, in the production of the porous reducing electrode support type electrolyte membrane 20, the electrolyte content of the electrolyte dispersion liquid in step 1 was set to 0.5 wt. I made it to%. All other conditions are the same as in Example 9.
  • Example 12 In Example 12, in the production of the porous reducing electrode-supported electrolyte membrane 20, the electrolyte content of the electrolyte dispersion in step 1 was 1.0 wt. I made it to%. All other conditions are the same as in Example 9.
  • Example 13 In Example 13, in the production of the porous reducing electrode-supported electrolyte membrane 20, the electrolyte content of the electrolyte dispersion in step 1 was 5.0 wt. I made it to%. All other conditions are the same as in Example 9.
  • Example 14 In Example 14, a copper porous body having a thickness of 1 mm and a porosity of 90% was used in the production of the porous reducing electrode-supported electrolyte membrane 20. The thickness of the porous reducing electrode 5 after thermocompression bonding was 0.2 mm, and the porosity was 50%. All other conditions are the same as in Example 9.
  • Example 15 In Example 15, a copper porous body having a thickness of 1 mm and a porosity of 85% was used in the production of the porous reducing electrode-supported electrolyte membrane 20.
  • the thickness of the porous reducing electrode 5 after thermocompression bonding was 0.2 mm, and the porosity was 25%. All other conditions are the same as in Example 9.
  • Example 16 In Example 16, a copper porous body having a thickness of 1 mm and a porosity of 81% was used in the production of the porous reducing electrode-supported electrolyte membrane 20. The thickness of the porous reducing electrode 5 after thermocompression bonding was 0.2 mm, and the porosity was 5%. All other conditions are the same as in Example 9.
  • FIG. 5 is a diagram showing a configuration of a carbon dioxide gas phase reducing device according to Comparative Target Example 1 corresponding to Examples 1 to 8.
  • the configuration of Comparative Example 1 is the same as that of the conventional carbon dioxide gas phase reducing device shown in FIG. 2 of Non-Patent Document 1.
  • the structure of the reduction tank 4 is different.
  • the oxidation tank 1 and the reduction tank 4 are separated from each other only by the electrolyte membrane 6.
  • a non-porous reduction electrode 5'without pores is inserted in the reduction tank 4.
  • the inside of the reduction tank 4 is filled with the aqueous solution 12 and the non-porous reduction electrode 5'is immersed.
  • a tube 13 is inserted into the reduction tank 4 in order to allow carbon dioxide to flow into the aqueous solution 12.
  • the aqueous solution 3 in the oxide tank 1 was a 1 mol / l sodium hydroxide aqueous solution.
  • the aqueous solution 12 of the reduction tank 4 was a 0.5 mol / l potassium hydrogen carbonate aqueous solution.
  • the non-porous reduction electrode 5' was installed by using a copper plate (manufactured by Niraco Co., Ltd.) having an area of about 6 cm 2 so as to be immersed in the aqueous solution 12.
  • Other configurations are the same as those in the first embodiment.
  • FIG. 6 is a diagram showing a configuration of a carbon dioxide gas phase reducing device according to Comparative Target Example 2 corresponding to Examples 9 to 16.
  • the structure of the reduction tank 4 is different.
  • the oxidation tank 1 and the reduction tank 4 are separated from each other only by the electrolyte membrane 6.
  • a non-porous reduction electrode 5'without pores is inserted in the reduction tank 4.
  • the inside of the reduction tank 4 is filled with the aqueous solution 12 and the non-porous reduction electrode 5'is immersed.
  • a tube 13 is inserted into the reduction tank 4 in order to allow carbon dioxide to flow into the aqueous solution 12.
  • the aqueous solution 3 in the oxide tank 1 was a 1 mol / l sodium hydroxide aqueous solution.
  • the aqueous solution 12 of the reduction tank 4 was a 0.5 mol / l potassium hydrogen carbonate aqueous solution.
  • the non-porous reduction electrode 5' was installed by using a copper plate (manufactured by Niraco Co., Ltd.) having an area of about 6 cm 2 so as to be immersed in the aqueous solution 12.
  • Other configurations are the same as in the ninth embodiment.
  • Table 1 shows the Faraday efficiency of the carbon dioxide reduction reaction according to Examples 1 to 16 and Comparative Examples 1 and 2.
  • Faraday efficiency is a value indicating the ratio of the current value used for each reduction reaction to the current value flowing between the electrodes at the time of light irradiation or voltage application, as shown in the equation (1).
  • the "current value of each reduction reaction” in the formula (1) can be obtained by converting the measured value of the amount of each reduction product produced into the number of electrons required for the production reaction.
  • the concentration of the reduction reaction product is A [ppm]
  • the flow rate of the carrier gas is B [L / sec]
  • the number of electrons required for the reduction reaction is Z [mol]
  • the Faraday constant is F [C / mol]
  • the molar of the gas It was calculated using the formula (2) when the body was Vm [L / mol].
  • the solution of the electrolyte dispersion 50 adheres to the surface of the porous reducing electrode 5, and the solution thereof adheres to the surface of the porous reducing electrode 5.
  • the electrolyte dispersion liquid 50 is transferred to the electrolyte membrane 60 with heating, so that the structure is such that the electrolyte membrane 60 is dispersed on the surface and inside of the porous reducing electrode 5.
  • the concentration of the electrolyte dispersion 50 is 1.0 wt. If it is more than%, the structure is such that the surface of the porous reducing electrode 5 is completely covered with the electrolyte membrane 60, so that carbon dioxide cannot be supplied to the surface of the porous reducing electrode 5.
  • the concentration of the electrolyte dispersion 50 is 0.05 wt. % -0.5 wt.
  • the electrolyte membrane 60 having a thickness of several ⁇ m is dispersed on the surface of the porous reduction electrode 5 and the interface between voids, and is covered in an island shape.
  • a large amount of a three-phase interface composed of [reducing electrode-electrolyte film-carbon dioxide] is formed in the porous reducing electrode 5, and the carbon dioxide reduction reaction proceeds at the three-phase interface to reduce carbon dioxide.
  • the efficiency of the reaction is improved. Therefore, the concentration of the electrolyte dispersion 50 used in step 1 is 1.0 wt. % Is considered preferable.
  • Examples 1 to 3 and Examples 6 to 8 and Examples 9 to 11 and Examples 14 to 16 greatly improved the Faraday efficiency of carbon dioxide reduction, respectively. It can be seen that the reduction reaction of carbon dioxide is selectively occurring. This is because in Examples 1 to 3 and Examples 6 to 8, and Examples 9 to 11 and 14 to 16, carbon dioxide in the gas phase is directly applied to the porous reducing electrode 5 without using an aqueous solution. By supplying carbon dioxide near the surface of the porous reducing electrode 5, carbon dioxide is reduced, the diffusion resistance of carbon dioxide is reduced, the amount of carbon dioxide supplied to the porous reducing electrode 5 is increased, and the porosity is further increased. It is considered that the factor is that the electrolyte film 60 is dispersed and formed on the surface of the quality reducing electrode 5 to increase the reaction field.
  • Oxidation tank 2 Oxidation electrode 3: Aqueous solution 4: Reduction tank 5: Porous reduction electrode 5': Non-porous reduction electrode 6: Electrolyte film 7: Lead wire 8: Tube 9: Gas input port 10: Light source 11: Power supply 12: Aqueous solution 13: Tube 20: Porous reducing electrode support type electrolyte membrane 30a, 30b: Copper plate 40a, 40b: Hot plate 50: Electrolyte dispersion 60: Electrolyte membrane 100: Gas phase reducing device for carbon dioxide

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Abstract

This gas-phase reduction apparatus 100 for carbon dioxide is provided with an oxidation vessel 1 which contains an oxidation electrode 2, a reduction vessel 4 which is arranged adjacent to the oxidation vessel 1 and into which carbon dioxide is supplied when the inside of the reduction vessel 4 is empty, and a porous reduction electrode-supported electrolyte membrane 20 which is arranged between the oxidation vessel 1 and the reduction vessel 4, in which the porous reduction electrode-supported electrolyte membrane 20 is a joined body that is formed by joining a porous reduction electrode 5 formed by dispersing a first electrode membrane in an inside void to a second electrolyte membrane 6, the second electrolyte membrane 6 is arranged on the oxidation vessel 1 side, the porous reduction electrode 5 is arranged on the reduction vessel 4 side and is connected to the oxidation electrode 2 through a conducting wire 7, and the reduction reaction of the carbon dioxide in the reduction vessel 4 is performed by the action of electrons flowing through the conducting wire 7.

Description

二酸化炭素の気相還元装置、および、多孔質還元電極支持型電解質膜の製造方法Gas phase reduction device for carbon dioxide and method for manufacturing a porous reduction electrode-supported electrolyte membrane
　本発明は、二酸化炭素の気相還元装置、および、多孔質還元電極支持型電解質膜の製造方法に関する。 The present invention relates to a carbon dioxide gas phase reducing device and a method for producing a porous reducing electrode-supported electrolyte membrane.
　従来、地球温暖化の防止やエネルギーの安定供給という観点から、二酸化炭素を還元する技術が注目されている。二酸化炭素を還元する還元装置としては、太陽光等の光エネルギーを印加して二酸化炭素を還元する人工光合成技術を利用した還元装置、外部から電気エネルギーを印加して二酸化炭素を還元する電解分解装置がある（非特許文献１～４参照）。 Conventionally, technologies that reduce carbon dioxide have been attracting attention from the viewpoint of preventing global warming and providing a stable supply of energy. As a reduction device that reduces carbon dioxide, a reduction device that uses artificial photosynthesis technology that applies light energy such as sunlight to reduce carbon dioxide, and an electrolytic decomposition device that reduces carbon dioxide by applying electrical energy from the outside. (See Non-Patent Documents 1 to 4).
　非特許文献１の図２には、光照射による二酸化炭素の気相還元装置が図示されている。左側の酸化槽と右側の還元槽との間に電解質膜を配置し、酸化槽と還元槽とをそれぞれ水溶液で満たす。酸化槽内に窒化ガリウム（ＧａＮ）の酸化電極を入れ、還元槽内に銅（Ｃｕ）の還元電極を入れて、酸化電極と還元電極とを導線で接続する。そして、酸化槽内の水溶液にヘリウム（Ｈｅ）を流入し、還元槽内の水溶液に二酸化炭素（ＣＯ２）を流入する。 FIG. 2 of Non-Patent Document 1 illustrates a carbon dioxide gas phase reduction device by light irradiation. An electrolyte membrane is placed between the oxidation tank on the left side and the reduction tank on the right side, and the oxidation tank and the reduction tank are each filled with an aqueous solution. An oxide electrode of gallium nitride (GaN) is placed in the oxide tank, a reduction electrode of copper (Cu) is placed in the reduction tank, and the oxide electrode and the reduction electrode are connected by a lead wire. Then, helium (He) flows into the aqueous solution in the oxidation tank, and carbon dioxide (CO 2 ) flows into the aqueous solution in the reduction tank.
　このとき、酸化電極に光を照射すると、酸化電極では電子・正孔対の生成および分離が生じ、水（Ｈ２Ｏ）の酸化反応により酸素（Ｏ２）およびプロトン（Ｈ＋）が生成する。そして、プロトンは電解質膜を介して還元槽へ移動し、酸化電極で発生した電子（ｅ－）は導線を介して還元電極へ移動する。その後、還元電極ではプロトンと電子との結合により水素（Ｈ２）が生成し、プロトンと電子と二酸化炭素とにより二酸化炭素の還元反応が引き起こされる。この二酸化炭素の還元反応により、エネルギー資源として活用される一酸化炭素、ギ酸、メタンなどが生成する。 At this time, when the oxide electrode is irradiated with light, electron / hole pairs are generated and separated in the oxide electrode, and oxygen (O 2 ) and protons (H + ) are generated by the oxidation reaction of water (H 2 O). .. Then, the protons move to the reduction tank via the electrolyte membrane, and the electrons (e − ) generated in the oxidation electrode move to the reduction electrode via the conducting wire. After that, hydrogen (H 2 ) is generated by the bond between protons and electrons in the reducing electrode, and the reduction reaction of carbon dioxide is caused by the protons, electrons and carbon dioxide. This reduction reaction of carbon dioxide produces carbon monoxide, formic acid, methane, etc., which are used as energy resources.
　従来の二酸化炭素の気相還元装置の場合、還元対象である二酸化炭素は、還元槽内の水溶液に溶解して還元電極に到達し、還元電極の表面で還元される。しかし、二酸化炭素の媒介手段として水溶液を用いるため、その水溶液に溶解可能な二酸化炭素の濃度に限界があり、また、水溶液内での二酸化炭素の拡散抵抗は大きいので、還元電極に対して供給可能な二酸化炭素の供給量には限界がある。 In the case of the conventional carbon dioxide gas phase reduction device, the carbon dioxide to be reduced dissolves in the aqueous solution in the reduction tank, reaches the reduction electrode, and is reduced on the surface of the reduction electrode. However, since an aqueous solution is used as a medium for carbon dioxide, there is a limit to the concentration of carbon dioxide that can be dissolved in the aqueous solution, and the diffusion resistance of carbon dioxide in the aqueous solution is large, so that it can be supplied to the reducing electrode. There is a limit to the amount of carbon dioxide that can be supplied.
　本発明は、上記事情に鑑みてなされたものであり、本発明の目的は、二酸化炭素の気相還元装置において、二酸化炭素の還元反応の効率を改善可能な技術を提供することである。 The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique capable of improving the efficiency of a carbon dioxide reduction reaction in a carbon dioxide gas phase reduction device.
　本発明の一態様の二酸化炭素の気相還元装置は、酸化電極を含む酸化槽と、前記酸化槽に隣接し、空の内部に二酸化炭素が供給される還元槽と、前記酸化槽と前記還元槽との間に配置された多孔質還元電極支持型電解質膜と、を備え、前記多孔質還元電極支持型電解質膜は、空隙内部に第１の電解質膜が分散して形成された多孔質還元電極と第２の電解質膜とを接合した接合体であり、前記第２の電解質膜は、前記酸化槽側に配置され、前記多孔質還元電極は、前記還元槽側に配置され、前記酸化電極に導線で接続され、前記導線に流れる電子により前記還元槽内の前記二酸化炭素と還元反応を行う。 The carbon dioxide gas phase reduction device according to one aspect of the present invention includes an oxide tank including an oxidation electrode, a reduction tank adjacent to the oxide tank and supplying carbon dioxide to the inside of the empty space, the oxide tank and the reduction. The porous reduction electrode-supporting electrolyte membrane is provided with a porous reduction electrode-supporting electrolyte membrane arranged between the tank and the porous reduction electrode-supporting electrolyte membrane, and the porous reduction electrode-supporting electrolyte membrane is formed by dispersing the first electrolyte membrane inside the voids. It is a bonded body in which an electrode and a second electrolyte membrane are joined, the second electrolyte membrane is arranged on the oxide tank side, the porous reduction electrode is arranged on the reduction tank side, and the oxidation electrode is arranged. Is connected to the carbon dioxide by a lead wire, and the electrons flowing through the lead wire carry out a reduction reaction with the carbon dioxide in the reduction tank.
　本発明の一態様の多孔質還元電極支持型電解質膜の製造方法は、酸化電極を含む酸化槽と空の内部に二酸化炭素が供給される還元槽との間に配置される多孔質還元電極支持型電解質膜の製造方法において、電解質膜を構成する高分子材料を分散させた電解質分散液に多孔質還元電極を含侵させる工程と、前記電解質分散液に含侵させた前記多孔質還元電極と電解質膜とを重ね、加熱しながら圧力を加えて接合させる工程と、を行う。 In the method for producing a porous reducing electrode support type electrolyte membrane according to one aspect of the present invention, the porous reducing electrode support is arranged between an oxide tank including an oxide electrode and a reduction tank in which carbon dioxide is supplied to the inside of the empty space. In the method for producing a type electrolyte membrane, a step of impregnating a porous reducing electrode into an electrolyte dispersion in which a polymer material constituting the electrolyte membrane is dispersed, and the porous reducing electrode impregnated in the electrolyte dispersion. The step of stacking the electrolyte membrane and applying pressure while heating to join them is performed.
　本発明によれば、二酸化炭素の気相還元装置において、二酸化炭素の還元反応の効率を向上可能な技術を提供できる。 According to the present invention, it is possible to provide a technique capable of improving the efficiency of the carbon dioxide reduction reaction in a carbon dioxide gas phase reduction device.
図１は、実施例１に係る二酸化炭素の気相還元装置の構成例を示す図である。FIG. 1 is a diagram showing a configuration example of a carbon dioxide gas phase reducing device according to Example 1. 図２は、多孔質還元電極支持型電解質膜の作製方法を示す図である。FIG. 2 is a diagram showing a method for producing a porous reducing electrode-supported electrolyte membrane. 図３は、多孔質還元電極内に電解質膜が分散形成された様子を示す図である。FIG. 3 is a diagram showing a state in which an electrolyte membrane is dispersed and formed in the porous reducing electrode. 図４は、実施例９に係る二酸化炭素の気相還元装置の構成例を示す図である。FIG. 4 is a diagram showing a configuration example of a carbon dioxide gas phase reducing device according to Example 9. 図５は、比較対象例１に係る二酸化炭素の気相還元装置の構成例を示す図である。FIG. 5 is a diagram showing a configuration example of a carbon dioxide gas phase reducing device according to Comparative Example 1. 図６は、比較対象例２に係る二酸化炭素の気相還元装置の構成例を示す図である。FIG. 6 is a diagram showing a configuration example of a carbon dioxide gas phase reducing device according to Comparative Example 2. 図７は、多孔質還元電極内に電解質膜が島状に分散形成された様子を示す図である。FIG. 7 is a diagram showing a state in which the electrolyte membrane is dispersed and formed in an island shape in the porous reducing electrode.
　以下、図面を参照して本発明の実施例を説明する。本発明は、後述の実施例に限定されるものではなく、本発明の趣旨を逸脱しない範囲内において変更を加えることが可能である。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the examples described later, and changes can be made without departing from the spirit of the present invention.
　［発明の概要］
　本発明の目的は、二酸化炭素の気相還元装置において、二酸化炭素の還元反応の効率を改善可能な技術を提供することにある。この目的を達成するため、本発明は、従来の二酸化炭素の気相還元装置に対し、次の特徴を備える。 [Outline of the invention]
An object of the present invention is to provide a technique capable of improving the efficiency of a carbon dioxide reduction reaction in a carbon dioxide gas phase reduction device. In order to achieve this object, the present invention has the following features as compared with the conventional carbon dioxide gas phase reducing device.
　第１の特徴は、還元槽内を気相の二酸化炭素で満たし、気相の二酸化炭素を還元電極に直接供給する。これにより、還元槽内において、二酸化炭素の濃度が増加し、二酸化炭素の拡散抵抗が低減する。その結果、還元電極への二酸化炭素の供給量が増加し、還元電極上での二酸化炭素の還元反応の効率を向上できる。 The first feature is that the inside of the reduction tank is filled with carbon dioxide in the gas phase, and the carbon dioxide in the gas phase is directly supplied to the reduction electrode. As a result, the concentration of carbon dioxide increases in the reduction tank, and the diffusion resistance of carbon dioxide decreases. As a result, the amount of carbon dioxide supplied to the reducing electrode is increased, and the efficiency of the carbon dioxide reduction reaction on the reducing electrode can be improved.
　この点、二酸化炭素の還元反応を実現するには、［電解質膜－還元電極－気相の二酸化炭素］からなる三相界面が必要であるが、第１の特徴を採用すると、還元槽内から水溶液がなくなり、プロトンは還元槽内の気相中を移動できない。また、気相の二酸化炭素は、気孔のない還元電極内を移動できない。その結果、二酸化炭素の還元反応を実現できなくなる。そこで、第２の特徴をさらに備える。 In this respect, in order to realize the carbon dioxide reduction reaction, a three-phase interface consisting of [electrolyte film-reducing electrode-gas phase carbon dioxide] is required. The aqueous solution runs out, and the protons cannot move in the gas phase in the reduction tank. Also, carbon dioxide in the gas phase cannot move in the reduction electrode without pores. As a result, the reduction reaction of carbon dioxide cannot be realized. Therefore, the second feature is further provided.
　第２の特徴は、還元電極を気孔のある多孔質還元電極とし、多孔質還元電極と電解質膜とを接合する。これにより、［電解質膜－多孔質還元電極－気相の二酸化炭素］からなる三相界面が形成されるので、還元槽内を気相の二酸化炭素で満たした場合であっても、多孔質還元電極上での二酸化炭素の気相還元の進行を実現できる。 The second feature is that the reducing electrode is a porous reducing electrode with pores, and the porous reducing electrode and the electrolyte membrane are joined. As a result, a three-phase interface consisting of [electrolyte film-porous reduction electrode-gas phase carbon dioxide] is formed, so that even when the inside of the reduction tank is filled with vapor phase carbon dioxide, porous reduction is performed. The progress of carbon dioxide gas phase reduction on the electrode can be realized.
　しかし、多孔質還元電極に対して電解質膜を接合させるだけでは、［電解質膜－多孔質還元電極－気相の二酸化炭素］からなる三相界面は、電解質膜と多孔質還元電極との接合面上のみに限定されてしまう。そこで、第３の特徴をさらに備える。 However, simply by bonding the electrolyte membrane to the porous reducing electrode, the three-phase interface consisting of [electrolyte membrane-porous reducing electrode-gas phase carbon dioxide] is the bonding surface between the electrolyte membrane and the porous reducing electrode. It will be limited to the top only. Therefore, it is further provided with a third feature.
　第３の特徴は、多孔質還元電極の空隙内部にも電解質膜を分散して形成する。これにより、二酸化炭素の気相還元反応の反応場が増大するので、多孔質還元電極上での二酸化炭素の還元反応の効率を向上できる。 The third feature is that the electrolyte membrane is dispersed and formed inside the voids of the porous reducing electrode. As a result, the reaction field of the carbon dioxide gas phase reduction reaction is increased, so that the efficiency of the carbon dioxide reduction reaction on the porous reducing electrode can be improved.
　つまり、本発明は、空隙内部に電解質膜が分散して形成された多孔質還元電極に電解質膜を接合した多孔質還元電極支持型電解質膜に対して、気相の二酸化炭素を直接供給することを特徴とする。この特徴により、還元電極上での二酸化炭素の還元反応の効率向上を実現できる。 That is, the present invention directly supplies carbon dioxide in the gas phase to the porous reducing electrode-supported electrolyte membrane in which the electrolyte membrane is bonded to the porous reducing electrode formed by dispersing the electrolyte membrane inside the voids. It is characterized by. Due to this feature, it is possible to improve the efficiency of the reduction reaction of carbon dioxide on the reduction electrode.
　［実施例１］
　　［二酸化炭素の気相還元装置の構成］
　図１は、実施例１に係る二酸化炭素の気相還元装置１００の構成例を示す図である。当該気相還元装置１００は、酸化電極への光照射により還元電極で二酸化炭素の還元反応を起こす還元装置（人工光合成装置）である。以下、単に気相還元装置１００という。 [Example 1]
[Construction of carbon dioxide gas phase reduction device]
FIG. 1 is a diagram showing a configuration example of the carbon dioxide gas phase reducing device 100 according to the first embodiment. The gas phase reduction device 100 is a reduction device (artificial photosynthesis device) that causes a reduction reaction of carbon dioxide at the reduction electrode by irradiating the oxidation electrode with light. Hereinafter, it is simply referred to as a gas phase reducing device 100.
　気相還元装置１００は、図１に示すように、一筐体の内部空間を二分することで形成された酸化槽１と還元槽４とを備える。酸化槽１は水溶液３で満たされ、水溶液３には半導体または金属錯体からなる酸化電極２が挿入される。酸化槽１に隣接する還元槽４には、その空の内部に二酸化炭素の気体または二酸化炭素を含む気体が満たされる。 As shown in FIG. 1, the gas phase reducing device 100 includes an oxidation tank 1 and a reduction tank 4 formed by dividing the internal space of one housing into two. The oxide tank 1 is filled with the aqueous solution 3, and the oxide electrode 2 made of a semiconductor or a metal complex is inserted into the aqueous solution 3. The reduction tank 4 adjacent to the oxidation tank 1 is filled with carbon dioxide gas or a gas containing carbon dioxide in the empty space.
　酸化電極２は、例えば、窒化物半導体、酸化チタン、アモルファスシリコン、ルテニウム錯体、レニウム錯体のような光活性やレドックス活性を示す化合物である。水溶液３は、例えば、炭酸水素カリウム水溶液、炭酸水素ナトリウム水溶液、塩化カリウム水溶液、塩化ナトリウム水溶液、水酸化ナトリウム水溶液、水酸化カリウム水溶液、水酸化ルビジウム水溶液、水酸化セシウム水溶液である。 The oxide electrode 2 is a compound that exhibits photoactivity and redox activity, such as a nitride semiconductor, titanium oxide, amorphous silicon, a ruthenium complex, and a rhenium complex. The aqueous solution 3 is, for example, a potassium hydrogen carbonate aqueous solution, a sodium hydrogen carbonate aqueous solution, a potassium chloride aqueous solution, a sodium chloride aqueous solution, a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, a rubidium hydroxide aqueous solution, or a cesium hydroxide aqueous solution.
　酸化槽１と還元槽４との間には、空隙内部に電解質膜（第１の電解質膜）が分散して形成された多孔質還元電極５と、電解質膜（第２の電解質膜）６と、を接合した多孔質還元電極支持型電解質膜２０が配置される。酸化槽１側には電解質膜６が配置され、還元槽４側には多孔質還元電極５が配置される。酸化電極２と多孔質還元電極５とは、導線７で接続される。 A porous reducing electrode 5 formed by dispersing an electrolyte membrane (first electrolyte membrane) in the voids and an electrolyte membrane (second electrolyte membrane) 6 are formed between the oxidation tank 1 and the reduction tank 4. The porous reducing electrode support type electrolyte membrane 20 to which the above is bonded is arranged. The electrolyte membrane 6 is arranged on the oxidation tank 1 side, and the porous reduction electrode 5 is arranged on the reduction tank 4 side. The oxide electrode 2 and the porous reduction electrode 5 are connected by a conducting wire 7.
　酸化槽１には、酸化槽１内の水溶液３にヘリウムを流入するため、チューブ８が挿入される。還元槽４には、還元槽４内に二酸化炭素を流入するため、還元槽４の底部に気体入力口９が形成される。さらに、気相還元装置１００を運転するため、光源１０が酸化電極２に対して対向配置される。光源１０は、例えば、キセノンランプ、擬似太陽光源、ハロゲンランプ、水銀ランプ、太陽光、または、これらの組み合わせである。 A tube 8 is inserted into the oxidation tank 1 in order to allow helium to flow into the aqueous solution 3 in the oxidation tank 1. Since carbon dioxide flows into the reduction tank 4, a gas input port 9 is formed at the bottom of the reduction tank 4. Further, in order to operate the gas phase reduction device 100, the light source 10 is arranged to face the oxide electrode 2. The light source 10 is, for example, a xenon lamp, a pseudo-solar light source, a halogen lamp, a mercury lamp, sunlight, or a combination thereof.
　　［多孔質還元電極支持型電解質膜の作製方法］
　多孔質還元電極支持型電解質膜２０の作製方法を説明する。多孔質還元電極支持型電解質膜２０は、多孔質還元電極５と電解質膜６とを接合して形成する。 [Method for producing porous reducing electrode-supported electrolyte membrane]
A method for producing the porous reducing electrode support type electrolyte membrane 20 will be described. The porous reducing electrode support type electrolyte membrane 20 is formed by joining the porous reducing electrode 5 and the electrolyte membrane 6.
　多孔質還元電極５は、例えば、銅、白金、金、銀、インジウム、パラジウム、ガリウム、ニッケル、スズ、カドミウム、それらの合金の多孔質体、酸化銀、酸化銅、酸化銅（ＩＩ）、酸化ニッケル、酸化インジウム、酸化スズ、酸化タングステン、酸化タングステン（ＶＩ）、酸化銅などの多孔質体である。その他、多孔質還元電極５は、金属イオンとアニオン性配位子とを有する多孔性金属錯体でもよい。 The porous reducing electrode 5 is, for example, copper, platinum, gold, silver, indium, palladium, gallium, nickel, tin, cadmium, a porous body of an alloy thereof, silver oxide, copper oxide, copper oxide (II), oxidation. It is a porous body such as nickel, indium oxide, tin oxide, tungsten oxide, tungsten oxide (VI), and copper oxide. In addition, the porous reducing electrode 5 may be a porous metal complex having a metal ion and an anionic ligand.
　電解質膜６は、例えば、炭素－フッ素からなる骨格を持つ電解質膜であるナフィオン（商標登録）、フォアブルー、アクイヴィオンである。その他、電解質膜６は、炭化水素系骨格を持つ電解質膜であるセレミオンやネオセプタでもよい。 The electrolyte membrane 6 is, for example, Nafion (trademark registration), Foreblue, and Aquivion, which are electrolyte membranes having a skeleton composed of carbon and fluorine. In addition, the electrolyte membrane 6 may be Celemion or Neosepta, which is an electrolyte membrane having a hydrocarbon-based skeleton.
　実施例１では、多孔質還元電極５として、厚み１ｍｍ、気孔率９８％の銅多孔質体を用いた。電解質膜６として、カチオン交換膜であるナフィオンを用いた。また、作製時に使用する電解質分散液には、デュポン社製のナフィオン分散液（商標登録）（ナフィオン含有率：２０ｗｔ．%）を、純水で２００倍に希釈してナフィオン含有率（＝電解質含有率）を０．０５ｗｔ．%に調製したナフィオン分散液を用いた。希釈に用いる溶媒は、例えば、純水もしくは低級アルコール、または、それらの混合液である。実施例１では、純水を用いた。 In Example 1, a copper porous body having a thickness of 1 mm and a porosity of 98% was used as the porous reducing electrode 5. As the electrolyte membrane 6, Nafion, which is a cation exchange membrane, was used. The electrolyte dispersion used during production is a Nafion dispersion (registered trademark) manufactured by DuPont (Nafion content: 20 wt.%) Diluted 200-fold with pure water to contain Nafion (= electrolyte content). Rate) is 0.05 wt. The Nafion dispersion prepared in% was used. The solvent used for dilution is, for example, pure water, a lower alcohol, or a mixture thereof. In Example 1, pure water was used.
　まず、電解質膜６のプロトン移動度を向上させるため、予め、電解質膜６を沸騰硝酸と沸騰純水とにそれぞれ浸漬させておく。次に、工程１として、多孔質還元電極５を、電解質膜を構成する高分子材料を分散させた電解質分散液（電解質含有率：０．０５ｗｔ．%）に含侵させる。その後、沸騰硝酸と沸騰純水とにそれぞれ浸漬させた電解質膜６の上に、電解質分散液に含侵させた多孔質還元電極５を重ね、図２に示すように、そのサンプルを２つの銅板３０ａ，３０ｂの間に配置する。次に、工程２として、このサンプルを熱圧着装置（ホットプレス機）のホットプレート４０ａ，４０ｂの間に設置し、加熱温度１５０℃の条件で加熱しながら、多孔質還元電極５の上面に対して垂直方向に下方へ（電極面に対して）圧力を加えて３分間放置する。その後、そのサンプルを素早く冷却して取り出す。これにより、多孔質還元電極５と電解質膜６とが接合した多孔質還元電極支持型電解質膜２０を得ることができる。なお、熱圧着後の多孔質還元電極５の厚みは０．２ｍｍ、気孔率は９０％であった。 First, in order to improve the proton mobility of the electrolyte membrane 6, the electrolyte membrane 6 is previously immersed in boiling nitric acid and boiling pure water, respectively. Next, as step 1, the porous reducing electrode 5 is impregnated with an electrolyte dispersion liquid (electrolyte content: 0.05 wt.%) In which a polymer material constituting an electrolyte membrane is dispersed. After that, the porous reducing electrode 5 impregnated with the electrolyte dispersion was placed on the electrolyte membrane 6 immersed in boiling nitric acid and boiling pure water, respectively, and the sample was placed on two copper plates as shown in FIG. It is arranged between 30a and 30b. Next, as step 2, this sample is placed between the hot plates 40a and 40b of the thermocompression bonding device (hot press machine), and while heating under the condition of a heating temperature of 150 ° C., it is applied to the upper surface of the porous reducing electrode 5. Apply pressure vertically downward (against the electrode surface) and leave it for 3 minutes. The sample is then quickly cooled and removed. As a result, it is possible to obtain the porous reducing electrode support type electrolyte membrane 20 in which the porous reducing electrode 5 and the electrolyte membrane 6 are bonded. The thickness of the porous reduction electrode 5 after thermocompression bonding was 0.2 mm, and the porosity was 90%.
　工程１において、多孔質還元電極５を電解質分散液に含侵しているため、図２の拡大図に示すように、多孔質還元電極５の表面および内部に電解質分散液５０の溶液が付着している。その状態で工程２の熱プレス処理を行うと、加熱と共に電解質分散液５０に含まれる低級アルコールや純水は気化し、電解質分散液に含まれるナフィオンのみがガラス転移して、厚みが数百ｎｍの電解質膜（ナフィオン膜）を形成することで、図３に示すように、多孔質還元電極５の表面および内部に電解質膜（第１の電解質膜）６０が分散形成される。多孔質還元電極５と電解質膜（第２の電解質膜）６との界面に分散形成される電解質膜６０によって両者が接着し、多孔質還元電極５の内部には分散形成された電解質膜６０と多孔質還元電極５と気相の二酸化炭素とからなる三相界面が形成されるため、二酸化炭素の気相還元反応の反応場が増大し、その三相界面において二酸化炭素の還元反応が効率よく進行する。 Since the porous reducing electrode 5 is impregnated in the electrolyte dispersion liquid in step 1, the solution of the electrolyte dispersion liquid 50 adheres to the surface and the inside of the porous reducing electrode 5 as shown in the enlarged view of FIG. There is. When the hot press treatment of step 2 is performed in this state, the lower alcohol and pure water contained in the electrolyte dispersion 50 are vaporized with heating, and only the naphthion contained in the electrolyte dispersion is transferred to the glass, and the thickness is several hundred nm. By forming the electrolyte membrane (Nafion membrane) of the above, as shown in FIG. 3, the electrolyte membrane (first electrolyte membrane) 60 is dispersed and formed on the surface and the inside of the porous reducing electrode 5. The electrolyte membrane 60 dispersedly formed at the interface between the porous reducing electrode 5 and the electrolyte membrane (second electrolyte membrane) 6 adheres to each other, and the electrolyte membrane 60 dispersedly formed inside the porous reducing electrode 5 Since a three-phase interface composed of the porous reduction electrode 5 and the carbon dioxide in the gas phase is formed, the reaction field of the gas phase reduction reaction of carbon dioxide is increased, and the reduction reaction of carbon dioxide is efficiently performed at the three-phase interface. proceed.
　　［電気化学測定およびガス・液体生成量測定］
　電気化学測定およびガス・液体生成量測定を説明する。 [Electrochemical measurement and gas / liquid production amount measurement]
Electrochemical measurement and gas / liquid production amount measurement will be described.
　酸化槽１を水溶液３で満たす。酸化電極２には、サファイア基板上にｎ型半導体である窒化ガリウム（ＧａＮ）の薄膜と、窒化アルミニウムガリウム（ＡｌＧａＮ）の薄膜とを、その順にエピタキシャル成長させ、その上にニッケル（Ｎｉ）を真空蒸着して熱処理を行うことで、酸化ニッケル（ＮｉＯ）の助触媒薄膜を形成した基板を用いた。そして、その酸化電極２を、水溶液３に浸水するように酸化槽１内に設置した。水溶液３は、１．０ｍｏｌ／Ｌの水酸化カリウム水溶液とした。光源１０には、３００Ｗの高圧キセノンランプ（波長４５０ｎｍ以上をカット、照度６．６ｍＷ／ｃｍ２）を用い、酸化電極２の半導体光電極の酸化助触媒が形成されている面（ＮｉＯの形成面）が照射面となるように固定した。酸化電極２の光照射面積を２．５ｃｍ２とした。 The oxidation tank 1 is filled with the aqueous solution 3. On the oxide electrode 2, a thin film of gallium nitride (GaN), which is an n-type semiconductor, and a thin film of aluminum gallium nitride (AlGaN) are epitaxially grown on a sapphire substrate in this order, and nickel (Ni) is vacuum-deposited on the thin film. A substrate on which a nickel oxide (NiO) co-catalyst thin film was formed was used by performing the heat treatment. Then, the oxidation electrode 2 was installed in the oxidation tank 1 so as to be immersed in the aqueous solution 3. The aqueous solution 3 was a 1.0 mol / L potassium hydroxide aqueous solution. A 300 W high-pressure xenon lamp (wavelength 450 nm or more cut, illuminance 6.6 mW / cm 2 ) is used as the light source 10, and the surface on which the oxidation assist catalyst of the semiconductor optical electrode of the oxide electrode 2 is formed (the surface on which NiO is formed). ) Was fixed so as to be the irradiation surface. The light irradiation area of the oxide electrode 2 was set to 2.5 cm 2 .
　酸化槽１に対してチューブ８からヘリウムを、還元槽４に対して気体入力口９から二酸化炭素を、それぞれ流量５ｍｌ／ｍｉｎかつ圧力０．１８ＭＰａで流し入れた。この系では、多孔質還元電極支持型電解質膜２０内の［電解質膜－銅（多孔質還元電極）－気相の二酸化炭素］からなる三相界面において、二酸化炭素の還元反応を進行させることができる。 Helium was poured into the oxidation tank 1 from the tube 8 and carbon dioxide was poured into the reduction tank 4 from the gas input port 9 at a flow rate of 5 ml / min and a pressure of 0.18 MPa, respectively. In this system, the carbon dioxide reduction reaction can proceed at the three-phase interface composed of [electrolyte membrane-copper (porous reduction electrode) -gas phase carbon dioxide] in the porous reduction electrode-supported electrolyte membrane 20. can.
　酸化槽１と還元槽４とをヘリウムと二酸化炭素とでそれぞれ十分に置換した後、光源１０を用いて酸化電極２に均一に光を照射した。酸化電極２への光照射により、酸化電極２と多孔質還元電極５との間に電子が流れる。光照射時の酸化電極２と多孔質還元電極５との間の電流値を、電気化学測定装置（Ｓｏｌａｒｔｒｏｎ社製、１２８７型ポテンショガルバノスタット）で測定した。また、光照射中の任意の時間に、酸化槽１内および還元槽４内のガスおよび液体を採取し、ガスクロマトグラフおよび液体クロマトグラフ、ガスクロマトグラフ質量分析計で反応生成物を分析した。その結果、酸化槽１内では、酸素が生成され、還元槽４内では、水素、一酸化炭素、ギ酸、メタン、メタノール、エタノール、エチレンが生成されていることを確認した。 After sufficiently replacing the oxidation tank 1 and the reduction tank 4 with helium and carbon dioxide, respectively, the oxide electrode 2 was uniformly irradiated with light using the light source 10. By irradiating the oxide electrode 2 with light, electrons flow between the oxide electrode 2 and the porous reduction electrode 5. The current value between the oxide electrode 2 and the porous reduction electrode 5 at the time of light irradiation was measured with an electrochemical measuring device (1287 type potato galvanostat manufactured by Solartron). In addition, the gas and liquid in the oxidation tank 1 and the reduction tank 4 were collected at an arbitrary time during light irradiation, and the reaction products were analyzed by a gas chromatograph, a liquid chromatograph, and a gas chromatograph mass spectrometer. As a result, it was confirmed that oxygen was generated in the oxidation tank 1 and hydrogen, carbon monoxide, formic acid, methane, methanol, ethanol and ethylene were produced in the reduction tank 4.
　［実施例２］
　実施例２では、多孔質還元電極支持型電解質膜２０の作製において、工程１の電解質分散液の電解質含有率を０．１ｗｔ．%にした。それ以外の条件はすべて実施例１と同様である。 [Example 2]
In Example 2, in the production of the porous reducing electrode-supported electrolyte membrane 20, the electrolyte content of the electrolyte dispersion in step 1 was set to 0.1 wt. I made it to%. All other conditions are the same as in Example 1.
　［実施例３］
　実施例３では、多孔質還元電極支持型電解質膜２０の作製において、工程１の電解質分散液の電解質含有率を０．５ｗｔ．%にした。それ以外の条件はすべて実施例１と同様である。 [Example 3]
In Example 3, in the production of the porous reducing electrode support type electrolyte membrane 20, the electrolyte content of the electrolyte dispersion liquid in step 1 was set to 0.5 wt. I made it to%. All other conditions are the same as in Example 1.
　［実施例４］
　実施例４では、多孔質還元電極支持型電解質膜２０の作製において、工程１の電解質分散液の電解質含有率を１．０ｗｔ．%にした。それ以外の条件はすべて実施例１と同様である。 [Example 4]
In Example 4, in the production of the porous reducing electrode support type electrolyte membrane 20, the electrolyte content of the electrolyte dispersion liquid in step 1 was 1.0 wt. I made it to%. All other conditions are the same as in Example 1.
　［実施例５］
　実施例５では、多孔質還元電極支持型電解質膜２０の作製において、工程１の電解質分散液の電解質含有率を５．０ｗｔ．%にした。それ以外の条件はすべて実施例１と同様である。 [Example 5]
In Example 5, in the production of the porous reducing electrode-supported electrolyte membrane 20, the electrolyte content of the electrolyte dispersion in step 1 was 5.0 wt. I made it to%. All other conditions are the same as in Example 1.
　［実施例６］
　実施例６では、多孔質還元電極支持型電解質膜２０の作製において、厚み１ｍｍ、気孔率９０％の銅多孔質体を用いた。熱圧着後の多孔質還元電極５の厚みは０．２ｍｍ、気孔率は５０％であった。それ以外の条件はすべて実施例１と同様である。 [Example 6]
In Example 6, a copper porous body having a thickness of 1 mm and a porosity of 90% was used in the production of the porous reducing electrode-supported electrolyte membrane 20. The thickness of the porous reducing electrode 5 after thermocompression bonding was 0.2 mm, and the porosity was 50%. All other conditions are the same as in Example 1.
　［実施例７］
　実施例７では、多孔質還元電極支持型電解質膜２０の作製において、厚み１ｍｍ、気孔率８５％の銅多孔質体を用いた。熱圧着後の多孔質還元電極５の厚みは０．２ｍｍ、気孔率は２５％であった。それ以外の条件はすべて実施例１と同様である。 [Example 7]
In Example 7, a copper porous body having a thickness of 1 mm and a porosity of 85% was used in the production of the porous reducing electrode-supported electrolyte membrane 20. The thickness of the porous reducing electrode 5 after thermocompression bonding was 0.2 mm, and the porosity was 25%. All other conditions are the same as in Example 1.
　［実施例８］
　実施例８では、多孔質還元電極支持型電解質膜２０の作製において、厚み１ｍｍ、気孔率８１％の銅多孔質体を用いた。熱圧着後の多孔質還元電極５の厚みは０．２ｍｍ、気孔率は５％であった。それ以外の条件はすべて実施例１と同様である。 [Example 8]
In Example 8, a copper porous body having a thickness of 1 mm and a porosity of 81% was used in the production of the porous reducing electrode-supported electrolyte membrane 20. The thickness of the porous reducing electrode 5 after thermocompression bonding was 0.2 mm, and the porosity was 5%. All other conditions are the same as in Example 1.
　［実施例９］
　　［二酸化炭素の気相還元装置の構成］
　図４は、実施例９に係る二酸化炭素の気相還元装置１００の構成を示す図である。当該二酸化炭素の気相還元装置１００は、気相の二酸化炭素の電解還元反応の装置（電解還元反応装置）である。以下、単に気相還元装置１００という。 [Example 9]
[Construction of carbon dioxide gas phase reduction device]
FIG. 4 is a diagram showing the configuration of the carbon dioxide gas phase reducing device 100 according to the ninth embodiment. The carbon dioxide gas phase reduction device 100 is an apparatus (electrolytic reduction reaction apparatus) for an electrolytic reduction reaction of carbon dioxide in the gas phase. Hereinafter, it is simply referred to as a gas phase reducing device 100.
　気相還元装置１００は、図４に示すように、一筐体の内部空間を二分することで形成された酸化槽１と還元槽４とを備える。酸化槽１は水溶液３で満たされ、水溶液３には半導体または金属錯体からなる酸化電極２が挿入される。酸化槽１に隣接する還元槽４には、その空の内部に二酸化炭素の気体または二酸化炭素を含む気体が満たされる。酸化電極２は、例えば、白金、金、銀、銅、インジウム、ニッケルである。水溶液３の具体例は、実施例１と同様である。 As shown in FIG. 4, the gas phase reducing device 100 includes an oxidation tank 1 and a reduction tank 4 formed by dividing the internal space of one housing into two. The oxide tank 1 is filled with the aqueous solution 3, and the oxide electrode 2 made of a semiconductor or a metal complex is inserted into the aqueous solution 3. The reduction tank 4 adjacent to the oxidation tank 1 is filled with carbon dioxide gas or a gas containing carbon dioxide in the empty space. The oxide electrode 2 is, for example, platinum, gold, silver, copper, indium, or nickel. Specific examples of the aqueous solution 3 are the same as in Example 1.
　酸化槽１と還元槽４との間には、空隙内部に電解質膜（第１の電解質膜）が分散して形成された多孔質還元電極５と、電解質膜（第２の電解質膜）６と、を接合した多孔質還元電極支持型電解質膜２０が配置される。酸化槽１側には電解質膜６が配置され、還元槽４側には多孔質還元電極５が配置される。酸化電極２と多孔質還元電極５とは、導線７で接続される。多孔質還元電極５と電解質膜６との各具体例は、実施例１と同様である。 A porous reducing electrode 5 formed by dispersing an electrolyte membrane (first electrolyte membrane) in the voids and an electrolyte membrane (second electrolyte membrane) 6 are formed between the oxidation tank 1 and the reduction tank 4. The porous reducing electrode support type electrolyte membrane 20 to which the above is bonded is arranged. The electrolyte membrane 6 is arranged on the oxidation tank 1 side, and the porous reduction electrode 5 is arranged on the reduction tank 4 side. The oxide electrode 2 and the porous reduction electrode 5 are connected by a conducting wire 7. Specific examples of the porous reducing electrode 5 and the electrolyte membrane 6 are the same as in Example 1.
　酸化槽１には、酸化槽１内の水溶液３にヘリウムを流入するため、チューブ８が挿入される。還元槽４には、還元槽４内に二酸化炭素を流入するため、還元槽４の底部に気体入力口９が形成される。さらに、気相還元装置１００を運転するため、電源１１が導線７に接続される。 A tube 8 is inserted into the oxidation tank 1 in order to allow helium to flow into the aqueous solution 3 in the oxidation tank 1. Since carbon dioxide flows into the reduction tank 4, a gas input port 9 is formed at the bottom of the reduction tank 4. Further, in order to operate the gas phase reduction device 100, the power supply 11 is connected to the lead wire 7.
　　［多孔質還元電極支持型電解質膜の作製方法］
　多孔質還元電極支持型電解質膜２０は、実施例１と同様の手順で作製する。 [Method for producing porous reducing electrode-supported electrolyte membrane]
The porous reducing electrode support type electrolyte membrane 20 is produced by the same procedure as in Example 1.
　　［電気化学測定およびガス・液体生成量測定］
　電気化学測定およびガス・液体生成量測定を説明する。 [Electrochemical measurement and gas / liquid production amount measurement]
Electrochemical measurement and gas / liquid production amount measurement will be described.
　酸化槽１を水溶液３で満たす。酸化電極２には、白金（ニラコ社製）を用いた。酸化電極２の表面積の約０．５５ｃｍ２が水溶液３に浸水するように酸化槽１内に設置した。水溶液３は、１．０ｍｏｌ／Ｌの水酸化カリウム水溶液とした。 The oxidation tank 1 is filled with the aqueous solution 3. Platinum (manufactured by Niraco) was used for the oxide electrode 2. About 0.55 cm 2 of the surface area of the oxidation electrode 2 was installed in the oxide tank 1 so as to be immersed in the aqueous solution 3. The aqueous solution 3 was a 1.0 mol / L potassium hydroxide aqueous solution.
　酸化槽１に対してチューブ８からヘリウムを、還元槽４に対して気体入力口９から二酸化炭素を、それぞれ流量５ｍｌ／ｍｉｎかつ圧力０．１８ＭＰａで流し入れた。この系では、多孔質還元電極支持型電解質膜２０内の［電解質膜－銅（多孔質還元電極）－気相の二酸化炭素］からなる三相界面において、二酸化炭素の還元反応を進行させることができる。二酸化炭素が直接供給される多孔質還元電極５の面積は、約６．２５ｃｍ２である。 Helium was poured into the oxidation tank 1 from the tube 8 and carbon dioxide was poured into the reduction tank 4 from the gas input port 9 at a flow rate of 5 ml / min and a pressure of 0.18 MPa, respectively. In this system, the carbon dioxide reduction reaction can proceed at the three-phase interface composed of [electrolyte membrane-copper (porous reduction electrode) -gas phase carbon dioxide] in the porous reduction electrode-supported electrolyte membrane 20. can. The area of the porous reducing electrode 5 to which carbon dioxide is directly supplied is about 6.25 cm 2 .
　酸化槽１と還元槽４とをヘリウムと二酸化炭素とでそれぞれ十分に置換した後、酸化電極２と多孔質還元電極５との間を電源１１を介して導線７でつなぎ、電圧２．５Ｖを印加して電子を流した。電圧２．５Ｖを印加した時の酸化電極２と多孔質還元電極５との間の電流値を、電気化学測定装置で測定した。また、電圧印加中の任意の時間に、酸化槽１内および還元槽４内のガスおよび液体を採取し、ガスクロマトグラフおよび液体クロマトグラフ、ガスクロマトグラフ質量分析計にて反応生成物を分析した。その結果、酸化槽１内では、酸素が生成され、還元槽４内では、水素、一酸化炭素、ギ酸、メタン、メタノール、エタノール、エチレンが生成されていることを確認した。 After sufficiently substituting the oxidation tank 1 and the reduction tank 4 with helium and carbon dioxide, respectively, the oxidation electrode 2 and the porous reduction electrode 5 are connected by a lead wire 7 via a power source 11, and a voltage of 2.5 V is applied. It was applied and electrons were flown. The current value between the oxide electrode 2 and the porous reduction electrode 5 when a voltage of 2.5 V was applied was measured by an electrochemical measuring device. In addition, the gas and liquid in the oxidation tank 1 and the reduction tank 4 were sampled at an arbitrary time while the voltage was applied, and the reaction products were analyzed by a gas chromatograph, a liquid chromatograph, and a gas chromatograph mass spectrometer. As a result, it was confirmed that oxygen was generated in the oxidation tank 1 and hydrogen, carbon monoxide, formic acid, methane, methanol, ethanol and ethylene were produced in the reduction tank 4.
　［実施例１０］
　実施例１０では、多孔質還元電極支持型電解質膜２０の作製において、工程１の電解質分散液の電解質含有率を０．１ｗｔ．%にした。それ以外の条件はすべて実施例９と同様である。 [Example 10]
In Example 10, in the production of the porous reducing electrode support type electrolyte membrane 20, the electrolyte content of the electrolyte dispersion liquid in step 1 was set to 0.1 wt. I made it to%. All other conditions are the same as in Example 9.
　［実施例１１］
　実施例１１では、多孔質還元電極支持型電解質膜２０の作製において、工程１の電解質分散液の電解質含有率を０．５ｗｔ．%にした。それ以外の条件はすべて実施例９と同様である。 [Example 11]
In Example 11, in the production of the porous reducing electrode support type electrolyte membrane 20, the electrolyte content of the electrolyte dispersion liquid in step 1 was set to 0.5 wt. I made it to%. All other conditions are the same as in Example 9.
　［実施例１２］
　実施例１２では、多孔質還元電極支持型電解質膜２０の作製において、工程１の電解質分散液の電解質含有率を１．０ｗｔ．%にした。それ以外の条件はすべて実施例９と同様である。 [Example 12]
In Example 12, in the production of the porous reducing electrode-supported electrolyte membrane 20, the electrolyte content of the electrolyte dispersion in step 1 was 1.0 wt. I made it to%. All other conditions are the same as in Example 9.
　［実施例１３］
　実施例１３では、多孔質還元電極支持型電解質膜２０の作製において、工程１の電解質分散液の電解質含有率を５．０ｗｔ．%にした。それ以外の条件はすべて実施例９と同様である。 [Example 13]
In Example 13, in the production of the porous reducing electrode-supported electrolyte membrane 20, the electrolyte content of the electrolyte dispersion in step 1 was 5.0 wt. I made it to%. All other conditions are the same as in Example 9.
　［実施例１４］
　実施例１４では、多孔質還元電極支持型電解質膜２０の作製において、厚み１ｍｍ、気孔率９０％の銅多孔質体を用いた。熱圧着後の多孔質還元電極５の厚みは０．２ｍｍ、気孔率は５０％であった。それ以外の条件は全て実施例９と同様である。 [Example 14]
In Example 14, a copper porous body having a thickness of 1 mm and a porosity of 90% was used in the production of the porous reducing electrode-supported electrolyte membrane 20. The thickness of the porous reducing electrode 5 after thermocompression bonding was 0.2 mm, and the porosity was 50%. All other conditions are the same as in Example 9.
　［実施例１５］
　実施例１５では、多孔質還元電極支持型電解質膜２０の作製において、厚み１ｍｍ、気孔率８５％の銅多孔質体を用いた。熱圧着後の多孔質還元電極５の厚みは０．２ｍｍ、気孔率は２５％であった。それ以外の条件は全て実施例９と同様である。 [Example 15]
In Example 15, a copper porous body having a thickness of 1 mm and a porosity of 85% was used in the production of the porous reducing electrode-supported electrolyte membrane 20. The thickness of the porous reducing electrode 5 after thermocompression bonding was 0.2 mm, and the porosity was 25%. All other conditions are the same as in Example 9.
　［実施例１６］
　実施例１６では、多孔質還元電極支持型電解質膜２０の作製において、厚み１ｍｍ、気孔率８１％の銅多孔質体を用いた。熱圧着後の多孔質還元電極５の厚みは０．２ｍｍ、気孔率は５％であった。それ以外の条件は全て実施例９と同様である。 [Example 16]
In Example 16, a copper porous body having a thickness of 1 mm and a porosity of 81% was used in the production of the porous reducing electrode-supported electrolyte membrane 20. The thickness of the porous reducing electrode 5 after thermocompression bonding was 0.2 mm, and the porosity was 5%. All other conditions are the same as in Example 9.
　［比較対象例１］
　図５は、実施例１～８に対応する比較対象例１に係る二酸化炭素の気相還元装置の構成を示す図である。比較対象例１の構成は、非特許文献１の図２に示された従来の二酸化炭素の気相還元装置と同様である。 [Comparison target example 1]
FIG. 5 is a diagram showing a configuration of a carbon dioxide gas phase reducing device according to Comparative Target Example 1 corresponding to Examples 1 to 8. The configuration of Comparative Example 1 is the same as that of the conventional carbon dioxide gas phase reducing device shown in FIG. 2 of Non-Patent Document 1.
　図１と比較して、還元槽４の構造が異なる。酸化槽１と還元槽４とは、電解質膜６のみによって隔てられている。還元槽４には、気孔のない非多孔質還元電極５’が挿入されている。還元槽４内は水溶液１２で満たされ、非多孔質還元電極５’が浸されている。水溶液１２に二酸化炭素を流入するため、還元槽４にチューブ１３が挿入されている。 Compared with FIG. 1, the structure of the reduction tank 4 is different. The oxidation tank 1 and the reduction tank 4 are separated from each other only by the electrolyte membrane 6. A non-porous reduction electrode 5'without pores is inserted in the reduction tank 4. The inside of the reduction tank 4 is filled with the aqueous solution 12 and the non-porous reduction electrode 5'is immersed. A tube 13 is inserted into the reduction tank 4 in order to allow carbon dioxide to flow into the aqueous solution 12.
　酸化槽１内の水溶液３は、１ｍｏｌ／ｌの水酸化ナトリウム水溶液とした。還元槽４の水溶液１２は、０．５ｍｏｌ／ｌの炭酸水素カリウム水溶液とした。また、非多孔質還元電極５’は、面積約６ｃｍ２の銅板（ニラコ社製）を用い、水溶液１２に浸水するように設置した。その他の構成は、実施例１と同様である。 The aqueous solution 3 in the oxide tank 1 was a 1 mol / l sodium hydroxide aqueous solution. The aqueous solution 12 of the reduction tank 4 was a 0.5 mol / l potassium hydrogen carbonate aqueous solution. Further, the non-porous reduction electrode 5'was installed by using a copper plate (manufactured by Niraco Co., Ltd.) having an area of about 6 cm 2 so as to be immersed in the aqueous solution 12. Other configurations are the same as those in the first embodiment.
　反応生成物を分析したところ、水素、一酸化炭素、ギ酸、メタン、エチレンが生成していることを確認した。 Analysis of the reaction products confirmed that hydrogen, carbon monoxide, formic acid, methane, and ethylene were produced.
　［比較対象例２］
　図６は、実施例９～１６に対応する比較対象例２に係る二酸化炭素の気相還元装置の構成を示す図である。 [Comparison target example 2]
FIG. 6 is a diagram showing a configuration of a carbon dioxide gas phase reducing device according to Comparative Target Example 2 corresponding to Examples 9 to 16.
　図４と比較して、還元槽４の構造が異なる。酸化槽１と還元槽４とは、電解質膜６のみによって隔てられている。還元槽４には、気孔のない非多孔質還元電極５’が挿入されている。還元槽４内は水溶液１２で満たされ、非多孔質還元電極５’が浸されている。水溶液１２に二酸化炭素を流入するため、還元槽４にチューブ１３が挿入されている。 Compared with FIG. 4, the structure of the reduction tank 4 is different. The oxidation tank 1 and the reduction tank 4 are separated from each other only by the electrolyte membrane 6. A non-porous reduction electrode 5'without pores is inserted in the reduction tank 4. The inside of the reduction tank 4 is filled with the aqueous solution 12 and the non-porous reduction electrode 5'is immersed. A tube 13 is inserted into the reduction tank 4 in order to allow carbon dioxide to flow into the aqueous solution 12.
　酸化槽１内の水溶液３は、１ｍｏｌ／ｌの水酸化ナトリウム水溶液とした。還元槽４の水溶液１２は、０．５ｍｏｌ／ｌの炭酸水素カリウム水溶液とした。また、非多孔質還元電極５’は、面積約６ｃｍ２の銅板（ニラコ社製）を用い、水溶液１２に浸水するように設置した。その他の構成は、実施例９と同様である。 The aqueous solution 3 in the oxide tank 1 was a 1 mol / l sodium hydroxide aqueous solution. The aqueous solution 12 of the reduction tank 4 was a 0.5 mol / l potassium hydrogen carbonate aqueous solution. Further, the non-porous reduction electrode 5'was installed by using a copper plate (manufactured by Niraco Co., Ltd.) having an area of about 6 cm 2 so as to be immersed in the aqueous solution 12. Other configurations are the same as in the ninth embodiment.
　反応生成物を分析したところ、水素、一酸化炭素、メタン、エチレン、ギ酸が生成していることを確認した。 Analysis of the reaction products confirmed that hydrogen, carbon monoxide, methane, ethylene, and formic acid were produced.
　［二酸化炭素の還元反応の実験結果］
　実施例１～１６および比較対象例１、２による二酸化炭素の還元反応のファラデー効率を表１に示す。 [Experimental results of carbon dioxide reduction reaction]
Table 1 shows the Faraday efficiency of the carbon dioxide reduction reaction according to Examples 1 to 16 and Comparative Examples 1 and 2.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　ファラデー効率とは、式（１）に示すように、光照射時または電圧印加時に電極間に流れた電流値に対して、各還元反応に使われた電流値の割合を示す値である。 Faraday efficiency is a value indicating the ratio of the current value used for each reduction reaction to the current value flowing between the electrodes at the time of light irradiation or voltage application, as shown in the equation (1).
　　各還元反応のファラデー効率＝（各還元反応の電流値）／（酸化電極－還元電極間の電流値）　・・・（１）
　式（１）の「各還元反応の電流値」は、各還元生成物の生成量の測定値を、その生成反応に必要な電子数に換算することで求めることができる。還元反応生成物の濃度をＡ［ｐｐｍ］、キャリアガスの流量をＢ［Ｌ／ｓｅｃ］、還元反応に必要な電子数をＺ［ｍｏｌ］、ファラデー定数をＦ［Ｃ／ｍｏｌ］、気体のモル体をＶｍ［Ｌ／ｍｏｌ］としたとき、式（２）を用いて算出した。 Faraday efficiency of each reduction reaction = (current value of each reduction reaction) / (current value between oxidation electrode and reduction electrode) ... (1)
The "current value of each reduction reaction" in the formula (1) can be obtained by converting the measured value of the amount of each reduction product produced into the number of electrons required for the production reaction. The concentration of the reduction reaction product is A [ppm], the flow rate of the carrier gas is B [L / sec], the number of electrons required for the reduction reaction is Z [mol], the Faraday constant is F [C / mol], and the molar of the gas. It was calculated using the formula (2) when the body was Vm [L / mol].
　　各還元反応の電流値［Ａ］＝（Ａ×Ｂ×Ｚ×Ｆ×１０－６）／Ｖｍ　・・・（２）
　表１より、実施例１～３は、実施例４，５と比較して、二酸化炭素還元の選択性が高いことを把握できる。実施例９～１１についても、実施例１２，１３と比較して、二酸化炭素還元の選択性が高いことを把握できる。 Current value of each reduction reaction [A] = (A × B × Z × F × 10-6 ) / Vm ・ ・ ・ (2)
From Table 1, it can be understood that Examples 1 to 3 have higher selectivity for carbon dioxide reduction than Examples 4 and 5. It can be understood that the selectivity of carbon dioxide reduction is higher in Examples 9 to 11 as compared with Examples 12 and 13.
　実施例５，１３については、二酸化炭素還元による生成物が検出されなかったため、ファラデー効率の測定結果は無しとなっている。これは、実施例４，５および実施例１２，１３において、電解質膜が多孔質還元電極５の金属表面を覆ってしまったことにより、多孔質還元電極５への二酸化炭素の供給が著しく不足したことが原因と考えられる。 In Examples 5 and 13, no product due to carbon dioxide reduction was detected, so there is no measurement result of Faraday efficiency. This is because, in Examples 4 and 5 and Examples 12 and 13, the supply of carbon dioxide to the porous reducing electrode 5 was significantly insufficient because the electrolyte membrane covered the metal surface of the porous reducing electrode 5. It is thought that this is the cause.
　また、図２および図３に示したように、工程１で多孔質還元電極５を電解質分散液に含侵させると、多孔質還元電極５の表面に電解質分散液５０の溶液が付着し、その状態で工程２の熱プレス処理を行うと、加熱と共に電解質分散液５０が電解質膜６０に転移することで、多孔質還元電極５の表面および内部に電解質膜６０が分散した構造となる。しかし、実施例４，５および実施例１２，１３のように、電解質分散液５０の濃度が１．０ｗｔ．％以上だと、多孔質還元電極５の表面を電解質膜６０で完全に被覆した構造になるため、二酸化炭素を多孔質還元電極５の表面に供給することができなくなる。 Further, as shown in FIGS. 2 and 3, when the porous reducing electrode 5 is impregnated into the electrolyte dispersion in step 1, the solution of the electrolyte dispersion 50 adheres to the surface of the porous reducing electrode 5, and the solution thereof adheres to the surface of the porous reducing electrode 5. When the hot press treatment of step 2 is performed in this state, the electrolyte dispersion liquid 50 is transferred to the electrolyte membrane 60 with heating, so that the structure is such that the electrolyte membrane 60 is dispersed on the surface and inside of the porous reducing electrode 5. However, as in Examples 4 and 5 and Examples 12 and 13, the concentration of the electrolyte dispersion 50 is 1.0 wt. If it is more than%, the structure is such that the surface of the porous reducing electrode 5 is completely covered with the electrolyte membrane 60, so that carbon dioxide cannot be supplied to the surface of the porous reducing electrode 5.
　一方、実施例１～３および実施例９～１１のように、電解質分散液５０の濃度が０．０５ｗｔ．％～０．５ｗｔ．％の場合には、図７に示すように、多孔質還元電極５の表面や空隙界面に厚み数μｍの電解質膜６０が分散して島状に被覆した構造となる。この構造では、［還元電極－電解質膜－二酸化炭素］からなる三相界面が多孔質還元電極５内に多量に形成され、その三相界面において二酸化炭素の還元反応が進行し、二酸化炭素の還元反応の効率が向上する。それ故、工程１で用いる電解質分散液５０の濃度は、１．０ｗｔ．％未満が好ましいと考えられる。 On the other hand, as in Examples 1 to 3 and Examples 9 to 11, the concentration of the electrolyte dispersion 50 is 0.05 wt. % -0.5 wt. In the case of%, as shown in FIG. 7, the electrolyte membrane 60 having a thickness of several μm is dispersed on the surface of the porous reduction electrode 5 and the interface between voids, and is covered in an island shape. In this structure, a large amount of a three-phase interface composed of [reducing electrode-electrolyte film-carbon dioxide] is formed in the porous reducing electrode 5, and the carbon dioxide reduction reaction proceeds at the three-phase interface to reduce carbon dioxide. The efficiency of the reaction is improved. Therefore, the concentration of the electrolyte dispersion 50 used in step 1 is 1.0 wt. % Is considered preferable.
　さらに、比較対象例１，２に対して、実施例１～３および実施例６～８と、実施例９～１１および実施例１４～１６とは、それぞれ、二酸化炭素還元のファラデー効率が大きく向上しており、二酸化炭素の還元反応が選択的に起こっていることがわかる。これは、実施例１～３および実施例６～８と、実施例９～１１および実施例１４～１６と、において、水溶液を介さず多孔質還元電極５に対して気相の二酸化炭素を直接供給することで、多孔質還元電極５の表面付近での二酸化炭素が増加し、二酸化炭素の拡散抵抗が低減され、多孔質還元電極５への二酸化炭素供給量が増加したこと、さらには、多孔質還元電極５の表面に電解質膜６０が分散して形成されて反応場が増大したこと、が要因と考えられる。 Further, with respect to Comparative Examples 1 and 2, Examples 1 to 3 and Examples 6 to 8 and Examples 9 to 11 and Examples 14 to 16 greatly improved the Faraday efficiency of carbon dioxide reduction, respectively. It can be seen that the reduction reaction of carbon dioxide is selectively occurring. This is because in Examples 1 to 3 and Examples 6 to 8, and Examples 9 to 11 and 14 to 16, carbon dioxide in the gas phase is directly applied to the porous reducing electrode 5 without using an aqueous solution. By supplying carbon dioxide near the surface of the porous reducing electrode 5, carbon dioxide is reduced, the diffusion resistance of carbon dioxide is reduced, the amount of carbon dioxide supplied to the porous reducing electrode 5 is increased, and the porosity is further increased. It is considered that the factor is that the electrolyte film 60 is dispersed and formed on the surface of the quality reducing electrode 5 to increase the reaction field.
　［発明の効果］
　本発明によれば、多孔質還元電極５に電解質膜６を接合した多孔質還元電極支持型電解質膜２０に対して、気相の二酸化炭素を直接的に供給するので、還元槽４の二酸化炭素の濃度が増加し、多孔質還元電極５の表面付近での二酸化炭素の拡散抵抗を低減できる。また、多孔質還元電極５の内部に電解質膜を分散して形成したので、二酸化炭素の気相還元反応の反応場が増大し、多孔質還元電極５での二酸化炭素の還元反応の効率向上を実現できる。さらに、工程１，２では、多孔質還元電極５の空隙率を詳細に制御でき、さらに多孔質還元電極５の内部に分散させる電解質分散液の量を規定できることから、反応場の制御が容易となる。 [Effect of the invention]
According to the present invention, carbon dioxide in the gas phase is directly supplied to the porous reducing electrode-supported electrolyte membrane 20 in which the electrolyte membrane 6 is bonded to the porous reducing electrode 5, so that the carbon dioxide in the reducing tank 4 is carbon dioxide. The concentration of carbon dioxide can be increased, and the diffusion resistance of carbon dioxide near the surface of the porous reducing electrode 5 can be reduced. Further, since the electrolyte film is dispersed and formed inside the porous reducing electrode 5, the reaction field of the gas phase reduction reaction of carbon dioxide is increased, and the efficiency of the carbon dioxide reduction reaction in the porous reducing electrode 5 is improved. realizable. Further, in steps 1 and 2, the porosity of the porous reducing electrode 5 can be controlled in detail, and the amount of the electrolyte dispersion liquid to be dispersed inside the porous reducing electrode 5 can be specified, so that the reaction field can be easily controlled. Become.
　１：酸化槽
　２：酸化電極
　３：水溶液
　４：還元槽
　５：多孔質還元電極
　５’：非多孔質還元電極
　６：電解質膜
　７：導線
　８：チューブ
　９：気体入力口
　１０：光源
　１１：電源
　１２：水溶液
　１３：チューブ
　２０：多孔質還元電極支持型電解質膜
　３０ａ，３０ｂ：銅板
　４０ａ，４０ｂ：ホットプレート
　５０：電解質分散液
　６０：電解質膜
　１００：二酸化炭素の気相還元装置 1: Oxidation tank 2: Oxidation electrode 3: Aqueous solution 4: Reduction tank 5: Porous reduction electrode 5': Non-porous reduction electrode 6: Electrolyte film 7: Lead wire 8: Tube 9: Gas input port 10: Light source 11: Power supply 12: Aqueous solution 13: Tube 20: Porous reducing electrode support type electrolyte membrane 30a, 30b: Copper plate 40a, 40b: Hot plate 50: Electrolyte dispersion 60: Electrolyte membrane 100: Gas phase reducing device for carbon dioxide

Claims (4)

  1. 　酸化電極を含む酸化槽と、
    　前記酸化槽に隣接し、空の内部に二酸化炭素が供給される還元槽と、
    　前記酸化槽と前記還元槽との間に配置された多孔質還元電極支持型電解質膜と、を備え、
    　前記多孔質還元電極支持型電解質膜は、
    　空隙内部に第１の電解質膜が分散して形成された多孔質還元電極と第２の電解質膜とを接合した接合体であり、前記第２の電解質膜は、前記酸化槽側に配置され、前記多孔質還元電極は、前記還元槽側に配置され、前記酸化電極に導線で接続され、前記導線に流れる電子により前記還元槽内の前記二酸化炭素と還元反応を行う二酸化炭素の気相還元装置。     An oxide tank containing an oxidation electrode and
    A reduction tank adjacent to the oxidation tank and supplying carbon dioxide to the inside of the sky,
    A porous reduction electrode-supported electrolyte membrane arranged between the oxidation tank and the reduction tank is provided.
    The porous reducing electrode support type electrolyte membrane is
    It is a bonded body in which a porous reducing electrode formed by dispersing a first electrolyte membrane inside a void and a second electrolyte membrane are joined, and the second electrolyte membrane is arranged on the oxide tank side. The porous reducing electrode is arranged on the reducing tank side, is connected to the oxidizing electrode by a lead wire, and undergoes a reduction reaction with the carbon dioxide in the reduction tank by electrons flowing through the lead wire. ..
  2. 　前記第１の電解質膜は、
    　前記多孔質還元電極の空隙界面に島状に形成されている請求項１に記載の二酸化炭素の気相還元装置。     The first electrolyte membrane is
    The gas phase reducing device for carbon dioxide according to claim 1, which is formed in an island shape at the void interface of the porous reducing electrode.
  3. 　酸化電極を含む酸化槽と空の内部に二酸化炭素が供給される還元槽との間に配置される多孔質還元電極支持型電解質膜の製造方法において、
    　電解質膜を構成する高分子材料を分散させた電解質分散液に多孔質還元電極を含侵させる工程と、
    　前記電解質分散液に含侵させた前記多孔質還元電極と電解質膜とを重ね、加熱しながら圧力を加えて接合させる工程と、
    　を行う多孔質還元電極支持型電解質膜の製造方法。     In the method for producing a porous reduction electrode-supported electrolyte membrane arranged between an oxidation tank containing an oxidation electrode and a reduction tank in which carbon dioxide is supplied to the inside of the empty space.
    The process of impregnating the porous reducing electrode into the electrolyte dispersion liquid in which the polymer material constituting the electrolyte membrane is dispersed, and
    A step of superimposing the porous reducing electrode impregnated in the electrolyte dispersion and the electrolyte membrane and applying pressure while heating to join them.
    A method for manufacturing a porous reduction electrode-supported electrolyte membrane.
  4. 　前記電解質分散液は、
    　電解質含有率が１．０ｗｔ．％未満である請求項３に記載の多孔質還元電極支持型電解質膜の製造方法。     The electrolyte dispersion liquid is
    The electrolyte content is 1.0 wt. The method for producing a porous reducing electrode-supported electrolyte membrane according to claim 3, wherein the content is less than%.
PCT/JP2020/044254 2020-11-27 2020-11-27 Gas-phase reduction apparatus for carbon dioxide, and method for producing porous reduction electrode-supported electrolyte membrane WO2022113277A1 (en)

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Publication number Priority date Publication date Assignee Title
WO2024116355A1 (en) * 2022-11-30 2024-06-06 日本電信電話株式会社 Carbon dioxide reduction apparatus

Citations (3)

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Publication number Priority date Publication date Assignee Title
JP2001097894A (en) * 1999-09-30 2001-04-10 Toshiba Corp Reduction apparatus for carbon dioxide gas
JP2017527701A (en) * 2014-09-08 2017-09-21 スリーエム イノベイティブ プロパティズ カンパニー Ionic polymer membrane for carbon dioxide electrolyzer
JP2019049043A (en) * 2017-09-07 2019-03-28 株式会社東芝 Membrane-electrode assembly, electrochemical cell, and electrochemical device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001097894A (en) * 1999-09-30 2001-04-10 Toshiba Corp Reduction apparatus for carbon dioxide gas
JP2017527701A (en) * 2014-09-08 2017-09-21 スリーエム イノベイティブ プロパティズ カンパニー Ionic polymer membrane for carbon dioxide electrolyzer
JP2019049043A (en) * 2017-09-07 2019-03-28 株式会社東芝 Membrane-electrode assembly, electrochemical cell, and electrochemical device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024116355A1 (en) * 2022-11-30 2024-06-06 日本電信電話株式会社 Carbon dioxide reduction apparatus

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